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Discussion Starter · #1 ·
Thinking of going with bigger tires but man those rpms will be really low. On my lb7 245 to 285 if i remember dropped my rpm 400 so 1550 at 60 now with the 6th gear would mean 1150 at 60 now don't ya think that is kindof low, just a thought maybe other of the answer.
 

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Thinking of going with bigger tires but man those rpms will be really low. On my lb7 245 to 285 if i remember dropped my rpm 400 so 1550 at 60 now with the 6th gear would mean 1150 at 60 now don't ya think that is kindof low, just a thought maybe other of the answer.
Umm, 520 ft. lbs at 1600 RPMs....I wouldn't worry about it, and I wonder if the RPMs will really drop that low. truck'll be workin' harder to turn the 285's...that's my opinion. Heck, I'd be more worried about 285's on stock wheels than about low RPMs.
JP
 

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Actually I think he has a 06, so, I am assuming a LBZ with 650 ft/lbs of torque. I wouldn't worry about it as long as the TC locks up. I guess you would have to drive around 70 then. I'm no expert, but as long as the transmission doesn't hunt between 5th and 6th, it shouldn't be a problem. There should be guys with them on already. It is only time until they chime in. BTW, I only got about a 200 RPM drop when I put the 285s on my LB7.
 

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I'll let you know. When I head for Texas in a couple of weeks and get out of this ice and snow crap (265 Studded), I am going to throw on my 285's for the trip to see how they work and how badly they affect mileage on a LBZ. May have to wait until I get to Reno to put them on if the weather doesn't clear. I am not worried about rpm's or power, just mpg which normally is about 3 mpg or more worse with 285's, at least on my 05 and 02 D/A's.
 

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06 LBZ with 6spd. 315 tires. 70mph=1650rpm.
 

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Actually I think he has a 06, so, I am assuming a LBZ with 650 ft/lbs of torque.
The original post said LB7 and without a sig I just assumed....oops. Anyways, if he has the LBZ, I really wouldn't have any worries...;) Also, if he has the LBZ then he has the tap select on the gear selector. He could always just select 5th if the trans starts huntin'.
JP
 

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1550 at 60 now? That's interesting... I checked mine today and I was running about 1450 at about 62 under a slight load. Pulled into manual and the selector was on 6th.
That's with BFG TA/KO 285's. The speedo (corrected with Bullydog) showed 60, but I need to correct a touch more as the GPS indicated 62.
 

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Discussion Starter · #9 ·
So what kindof milage is one getting with 285's with a lbz, not like it matters mine is only getting 13.5 now with 1500 miles on it bone stock.
 

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Wow, only 13.5! I'm averaging between 15-16 in the city with some highway. I thought that was bad. Hopefully when the intake and programmers come out along with my MBRP exhaust that I'm installing next week, I hope that it improves.
 

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http://personal.linkline.com/rlockyer/2500Gas.xls

LLY, not LBZ
Columns showing both calculated and corrected for the tire size.
If you are hand-calculating 13.5 based on actual odometer readings, then using a GPS you would be closer to 14.5 (7.8% theoetical difference).

I need to get the last couple of fill-ups in there.
The exhaust and Bullydog tuner have NOT helped :D

I'm considering backing down from "Performance" to the "Tow/Economy" tune. Main reason I bought it is to correct the odometer.
 

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So what kindof milage is one getting with 285's with a lbz, not like it matters mine is only getting 13.5 now with 1500 miles on it bone stock.
Mine didn't do well when Ifirst bought it, but after Iput some miles on it the mileage picked up. See what happens after 5K & 10K miles are on it. Also keep in mind that you are running 285s...that's bound to cost you some mileage(more weight & rolling resistence).
JP
 

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Discussion Starter · #13 ·
no no no guys sorry for the confusion the reason why I started this thread was to see if it's a good idea to run 285's with the low rpms with the new 6 speed alli and what the milage will suffer and when I said "13.5mpg bone stock" I mean it all the way to the tires, still running 245/75 sorry for the confusion. Thanks for all the info.
 

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no no no guys sorry for the confusion the reason why I started this thread was to see if it's a good idea to run 285's with the low rpms with the new 6 speed alli and what the mileage will suffer and when I said "13.5mpg bone stock" I mean it all the way to the tires, still running 245/75 sorry for the confusion. Thanks for all the info.
Well your mileage may suffer, but not because of low RPMs. In my opinion fuel mileage will suffer due to the heavier weight and higher rolling resistance of the 285's. Also, as the truck breaks-in, your mileage will increase, mine did, and now with 38K on it I'm getting about 15.5 mpg around town....and mine is a 4x4 dually....:D
JP
 
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